Flash proxy facilitator should not give IPv6 addresses to IPv4 proxies
The facilitator understands IPv4 and IPv6 client addresses. It should avoid giving an IPv6 client address to an IPv4-only proxy. Perhaps a reasonable heuristic is to only give IPv6 client addresses to proxies that talk to the facilitator over IPv6. It may be okay to assume that IPv6 proxies also support IPv4 (but also may not buy us much as long as IPv4 far outnumbers IPv6).